Healthy women warned over egg freezing

Healthy women should not rely on freezing their eggs as a way of preserving their fertility, a leading US fertility organisation is warning. Meanwhile, the largest study to date of children born from frozen eggs suggests the procedure does not threaten child health as feared.

There is “extraordinarily limited” data on the rate of successful pregnancies from egg freezing, said Marc Fritz, chair of the ASRM expert committee issuing the warning at the society’s annual meeting in Washington, DC, US.

However, the results of a new study – released at the same meeting – reviewing data about 550 children produced from egg freezing provides some reassurance that the procedure does not carry an increased risk of causing genetic damage leading to congenital abnormalities.

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Ice damage

The study found that 1% of the infants conceived and born from frozen eggs suffered from birth defects – a level comparable with that found in the general population.

Human egg cells are between 10 and 15 times larger than other cells in the body and so contain more water. As a consequence they sometimes fail to survive being frozen because destructive ice crystals form within the eggs as temperatures drop. To overcome this, experts either cool down eggs very gradually in the so-called “slow freezing” technique, or flash-freeze them in less than one second using a process known as “vitrification”.

The first child to be born from a frozen egg was in 1986, and since then a number of changes to the procedure – including the manual injection of sperm inside the egg, known as ICSI (intracytoplasmic sperm injection) – have dramatically improved the chances of a live birth from frozen eggs.

But not every egg survives the freezing and thawing process. And even then, experts estimate that each successfully thawed egg has only a 2% to 4% chance of producing a live birth. The procedure is also expensive – obtaining and freezing a dozen or so eggs costing about &dollar;10,000 dollars. Patients must then pay to keep their eggs on ice, and later spend further thousands of dollars on implantation.

Miscarriage risk

To address this concern, Ilan Tur-Kaspa, president of the Institute for Human Reproduction in Chicago, Illinois, US, and colleagues reviewed more than 100 published papers providing data on 750 pregnancies resulting in 550 live births from frozen eggs worldwide since 1986.

Their review identified five babies with birth defects among the more than 450 children for which health status was reported. The rate of congenital abnormalities they found – 0.9% – is comparable with that seen among children conceived naturally, according to Tur-Kaspa.

The abnormalities observed among the children born from frozen eggs include complications such as Turner syndrome and congenital heart defects.

Tur-Kaspa notes that there is a miscarriage rate of about 20% among women using frozen eggs. “It’s within the range of what you see in in-vitro fertilisation and ICSI” techniques, he says, noting that the higher age of women opting for all of these procedures translates into this miscarriage rate.

The ASRM committee stressed that while putting eggs on ice might be a suitable option for cancer patients facing a risk of ovarian failure, the technique should not be marketed to healthy women as a means to defer childbearing.

“Egg trauma”

Fritz stresses that frozen eggs are “traumatised at least twice – by freezing and by subsequent thawing”, and that this means that the procedure often fails to produce a viable embryo.

He worries that healthy women who elect to freeze their eggs have the false impression that it ensures their chances of bearing a child later on in life. He stresses that fertility centres need to explain to patients that the procedure is highly experimental.

“Although significant research has been undertaken, and babies are being born from these new techniques, caution and counselling are imperative at this stage, and for several years to come,” adds Simon Fishel, managing director of the CARE Fertility Group, in the UK.